DataAssist is not a Database.
DataAssist is a Dreamweaver extension, like eCart, that is used to create pages for managing and displaying information in the database.
you will probably need both DataAssist and the eCommerse mySQL Database.
Use Data Assist for crating the product Display pages that you will add eCart to as well as pages for entering product data into the eCommerse mySQL Database.
see the DataAssist support page for tutorials on creating the store admin backend:
You will also want to use the security assist extension to secure the admin backend pages.